[gtk+] Fix distcheck

[Matthias Clasen <matthiasc src gnome org>]

commit 31490b563410a7d3c32c8ddfb88f556cf78250dc
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Apr 28 10:12:21 2015 -0400

    Fix distcheck

 docs/reference/gtk/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gtk/Makefile.am b/docs/reference/gtk/Makefile.am
index afee620..b3f6dbd 100644
--- a/docs/reference/gtk/Makefile.am
+++ b/docs/reference/gtk/Makefile.am
@@ -299,6 +299,7 @@ content_files =                                     \
        gtk-encode-symbolic-svg.xml             \
        gtk-launch.xml                          \
        broadwayd.xml                           \
+       gtk-builder-tool.xml                    \
        input-handling.xml                      \
        visual_index.xml                        \
        getting_started.xml                     \